Motion planning for a conventional single-car elevator system, in which one car moves in one elevator shaft, is relatively simple. The elevator car services all requests in a current direction, then reverses and does the same again. However, in some elevator systems, multiple elevator cars move within one elevator shaft. Such systems reduce the number of elevator shafts, and increase the passenger capacity of the elevator systems.
Motion planning for the elevators cars moving in one shaft must prevent collision of the cars. One solution to the collision problem is to move both cars at the same time and in the same direction. Typically, such a solution is implemented in a “double-deck” elevator by arranging one elevator car on top of the other. The double-deck elevator allows passengers on two consecutive floors to use the elevator simultaneously, and significantly increase the passenger capacity of the elevator system. However, the double-deck elevator is only efficient in a building where the volume of traffic normally causes a single elevator to stop at every floor.
Another solution to the collision problem is to designate separate segments of the shaft for each elevator car. However, that approach restricts the flexibility of movement of each elevator car, and thus inefficient. At present, there is not enough computing power in real-time systems to search the space of all motion plans for large group elevator installations.
Accordingly, it is desired to provide a motion planning method for an elevator system that has multiple cars moving independently in one elevator shaft, while eliminating a possibility of collision.